1. Field of the Invention
The present invention relates generally to methods and systems for the accelerated drying of produce and for drying films on produce for food preservation purposes, and more particularly to accelerated drying methods and systems that are used to eliminate or reduce pathogens on the outermost surface layers of the produce during the drying process, and to simultaneously dry a protective coating or film on the produce, which film may be formed from a solute-laden slurry applied to the external surface of an item of produce during a washing step or thereafter.
2. Discussion of the Related Art
The freshness of fruits and vegetables, generally referred to as produce, is typically defined by the qualities of taste, texture and appearance. Due to certain physiological effects, produce generally begins to deteriorate and lose its freshness at the time of harvest. Once severed from the parent plant, produce no longer has the natural life-sustaining nutrients and fluids and the immune-like system of the plant to combat bacteria, fungi, viruses, and other pathogens which eventually deteriorate the produce. A significant percentage of most produce harvested for shipment and consumption at distant locations are thus lost due to such deterioration. Because of the immense size of the produce industry, it would be highly advantageous from an economic standpoint to preserve recently harvested produce in its fresh, savory condition for an extended period of time. Others have long recognized this. Hence, many different methods for extending produce shelf life have been developed.
Refrigeration has been the most popular method of increasing the useful life of fresh produce. By storing produce at a suitably low temperature, it is possible to extend the freshness by retarding ripening, softening, textural changes and color changes. Lower temperatures also reduce undesirable metabolic changes and moisture losses, and help prevent or slow undesirable pathogen growth on the produce. However, depending on the length of time and degree to which the produce is chilled, refrigeration generally adversely affects taste and quality. Not all produce can be successfully refrigerated to low temperatures. Excessive chilling, particularly at near freezing temperatures, can actually damage most types of produce. Even moderate chilling will interfere with the ripening processes of certain produce, such as bananas.
Other methods of extending produce shelf life include coating the produce with a protective material, such as wax. However, the success of the coating is related not only to how well the coating protects the produce, but also how well it maintains a desirable appearance of the produce, without affecting its taste. Consequently, the success of this method has been limited. It has also been attempted to lengthen the shelf life of produce through heating to reduce the microorganism population, then refrigerating it at a desirable temperature. The success of this process has been limited in that shelf life has not been significantly increased. It is also known to harvest produce prior to ripening, and then treat the produce with a ripening agent, such as ethylene gas, to effect ripening. This process has generally provided a low quality, unflavorful product, particularly in the case of tomatoes. Furthermore, the deterioration process begins at the time of harvest regardless of ripeness of the produce.
A more recent approach to extending the shelf life of produce, and tomatoes in particular, has been the employment of genetic engineering techniques to decrease the rate in which tomatoes are affected by at least selected types of microorganisms. Such a process can be viewed as overly complicated to accomplish the goals of extended freshness, and has also enjoyed only limited success. Additionally, certain countries prohibit or strictly regulate the growth, sale, and distribution of genetically altered or modified produce, thus cutting off potential markets to produce growers and distributors.
Another approach to extending produce shelf life is described in U.S. Pat. No. 5,229,152 (the ""152 patent) and U.S. Pat. No. 5,364,648 (the ""648 patent) issued to Meldrum, the entire specifications of which are expressly incorporated herein by reference. The ""152 and ""648 patents describe a method and apparatus for increasing the shelf life of produce by employing a xe2x80x9csnap freezingxe2x80x9d procedure. By xe2x80x9csnap freezingxe2x80x9d it is meant subjecting the produce to temperatures substantially at or below the freezing point of water for a very brief predetermined period of time without the produce flesh being frozen. The method described in the ""152 and ""648 patents include the step of first introducing an item of produce into a heated bath being vibrated generally at a frequency within the range of subsonic to ultrasonic frequencies for a predetermined time, preferably shortly after harvest, to clean the produce. Next, the item of produce is transferred to a nucleation vat containing a natural slurry generally comprising natural material extracts including predetermined concentrations and combinations of byproducts from the fruit or vegetable being processed, low solute concentrations of sucrose sugars, fruit and/or acetic acids, enzymes, and a water solvent carrier. The slurry is referred to as xe2x80x9csolute-laden,xe2x80x9d in that the slurry is substantially concentrated with various solutes, especially sugars, enzymes, and acids, in the liquid solvent, such as water. The slurry also has a relatively high moisture content.
The slurry is maintained at a temperature below the freezing point of water in order to snap freeze the item of produce. The item of produce is then xe2x80x9csnap frozenxe2x80x9d by immersing it in the cold slurry for a brief predetermined period of time. Because the item of produce is held in the nucleation vat for only a brief period of time, the flesh of the item of produce itself will not actually be frozen. Finally, the item of produce is transferred from the nucleation vat to an incubation chamber and held there for a predetermined time, generally at ambient temperatures. This incubation, or drying, stage is used to stabilize and dry the item of produce in order to fully dry and crystallize a film of the slurry on the outer surface of the item of produce. The film includes amorphous crystalline structures and/or microcrystalline structures that are formed on the outer surface of the item of produce, for example, along and within the external surfaces of the pores of the item of produce. This dried film substantially protects the produce from external pathogens, such as bacteria and fungi. The incubation stage generally takes from tens of minutes to several hours, and even as long as 48 hours. The item of produce can then be stored or displayed for extended periods of time without significant deterioration or loss of taste, texture and appearance, or the need for refrigeration.
Although the methodology disclosed in the ""152 and ""648 patents has increased the shelf life of produce as compared to previous conventional methods, an incubation period of even several minutes per item of produce is generally not preferred by produce growers, processors and distributors from a volume or efficiency standpoint. This is due, in large part, to the advent of highly rapid and mechanized produce processing operations, with the resultant increase in production volume requirements and decrease in the amount of time that produce can economically stay on drying conveyors or racks.
Therefore, the need still exists for methods and apparatus capable of rapidly and effectively accelerating the drying process used to dry a coating such as film on produce, and to simultaneously eliminate or at least reduce the pathogens present on the produce and/or in a coating or film, so that the produce will be better protected against internal and external pathogens, and will also be made ready for quicker packaging and distribution. There is a related need for accelerated the methods and systems for drying produce which are suitable for drying a film on produce that is formed from a solute-laden slurry previously applied to the outer surface of the produce, so as to crystallize that layer to form a protective barrier against external pathogens.
Therefore it is an object of the present invention to provide new and improved methods of and systems for extending the shelf life of produce by eliminating or at least reducing the number of pathogens found on the uppermost layers of harvested produce.
It is another object of the present invention to provide new and improved methods and systems of rapidly drying a film made up of a solute-laden slurry layer applied to the external surface of an item of produce, and in so drying the slurry layer, produce desirable crystallized structures within the dried film.
It is another object of the present invention to provide new and improved methods and systems of accelerating the drying of a solute-laden slurry layer applied to the external surface of an item of produce.
In order to overcome the aforementioned disadvantages and achieve many of the aforementioned objects of the present invention, there is provided, in accordance with a first aspect of the present invention, a first method of extending the shelf life of harvested produce. This method involves removing pathogens from the outermost layer of the produce. The method comprises the steps of:
(1) subjecting the produce to a first treatment procedure which includes applying a first mechanical force to the outermost surface layer of produce;
(2) subjecting the produce to a second treatment procedure, wherein the second treatment procedure includes directing electromagnetic energy in a first range of frequencies from at least a first radiant energy source to at least the outermost surface layer of produce; and
(3) subjecting the produce to a third treatment procedure, wherein the third treatment procedure includes applying heat energy from at least a first heat energy source to at least the outermost surface layer of produce. Each of the steps is preferably performed in a way that removes or neutralizes pathogens or at least helps slow down their growth, as will be further described below.
In accordance with a second aspect of the present invention, there is provided a second method of extending the shelf life of harvested produce. This method is preferably utilized after the washing the produce with a solution which includes water. This method works by removing pathogens from the outermost layer of the produce during the drying of the produce after washing. This second comprises the steps of:
(1) subjecting the produce to a first drying procedure, wherein at least a portion of any excess water from the washing is removed, wherein the first drying procedure includes applying a first mechanical force to the outermost surface layer of produce;
(2) subjecting the produce to a second drying procedure, wherein at least a portion of the moisture remaining on the outermost surface layer of the produce is removed, wherein the second drying procedure includes directing electromagnetic energy in a first range of frequencies from at least a first radiant energy source to at least the outermost surface layer of produce; and
(3) subjecting the produce to a third drying procedure, wherein at least a portion of the moisture remaining on the outermost surface layer of the produce is removed, wherein the third drying procedure includes applying heat energy from at least a first heat energy source to at least the outermost surface layer of produce.
In accordance with a third aspect of the present invention, a third method of extending the shelf life of produce is provided. This method is designed for use with produce, which either from a previous washing step or dipping step, has a solute-laden slurry layer containing water applied to at least a portion of the outermost surface thereof. This third method comprises the steps of:
(1) subjecting the produce to a first drying procedure, wherein at least a portion of the moisture in the solute-laden slurry layer is removed to form a moisture-reduced slurry layer on the produce, wherein the first drying procedure includes applying a stream of air and a vibratory force to the produce;
(2) subjecting the produce to a second drying procedure, wherein at least a portion of the moisture in the moisture-reduced slurry layer is removed to form a protective stratum on the produce, wherein the second procedure includes applying the energy from at least one energy source to the produce; and
(3) subjecting the produce to a third drying procedure, wherein at least a portion of the moisture in the protective stratum is removed to form a protective crystalline structure on the produce, wherein the third drying procedure includes applying the energy from at least one energy source to the produce.
In accordance with a fourth aspect of the present invention, a fourth method of extending the shelf life of produce is provided, wherein the produce has a solute-laden slurry layer applied to at least a portion of the external surface thereof, comprising: (1) subjecting the produce to a first drying procedure, wherein at least a portion of the moisture in the solute-laden slurry layer is removed to form a moisture-reduced slurry layer on the produce; (2) subjecting the produce to a second drying procedure, wherein at least a portion of the moisture in the moisture-reduced slurry layer is removed to form a protective stratum on the produce; and (3) subjecting the produce to a third drying procedure, wherein at least a portion of the moisture in the protective stratum is removed to form a protective film on the produce, which film preferably includes crystalline structural components.
In accordance with a fifth aspect of the present invention, a fifth method of extending the shelf life of produce is provided. In this method, the produce has a solute-laden slurry layer applied to at least a portion of the external surface thereof before the process is begun. This fifth method comprises:
(1) subjecting the produce to a first drying procedure, wherein at least a portion of the moisture in the solute-laden slurry layer is removed to form a moisture-reduced slurry layer on the produce, wherein the first drying procedure includes applying a stream of air to the produce;
(2) subjecting the produce to a second drying procedure, wherein at least a portion of the moisture in the moisture-reduced slurry layer is removed to form a protective stratum on the produce, wherein the second procedure includes applying the energy from at least one energy source to the produce; and
(3) subjecting the produce to a third drying procedure, wherein at least a portion of the moisture in the protective stratum is removed to form a protective film, preferably including crystalline structures on the produce, wherein the third drying procedure includes applying the energy from at least one energy source to the produce.
In accordance with a sixth aspect of the present invention, there is provided a sixth method of extending the shelf life of produce. Again, the produce already has a solute-laden slurry layer applied to at least a portion of the external surface thereof. The sixth method comprises the steps of:
(1) subjecting the produce to a first drying procedure, wherein at least a portion of the moisture in the solute-laden slurry layer is removed to form a moisture-reduced slurry layer on the produce, wherein the first drying procedure includes applying a vibratory force to the produce;
(2) subjecting the produce to a second drying procedure, wherein at least a portion of the moisture in the moisture-reduced slurry layer is removed to form a protective stratum on the produce, wherein the second drying procedure includes applying energy from at least one energy source to the produce; and
(3) subjecting the produce to a third drying procedure, wherein at least a portion of the moisture in the protective stratum is removed to form a protective film on the produce, which film preferably includes crystalline components wherein the third drying procedure includes applying the energy from at least one energy source to the produce.
In accordance with a seventh aspect of the present invention, a seventh method of extending the shelf life of produce is provided. As in some of the previous methods, the produce has a solute-laden slurry layer applied to at least a portion of the external surface thereof. The method comprises the steps of:
(1) subjecting the produce to a first drying procedure, wherein at least a portion of the moisture in the solute-laden slurry layer is removed to form a moisture-reduced slurry layer on the produce, wherein the first drying procedure includes applying a stream of air and a vibratory force to the produce;
(2) subjecting the produce to a second drying procedure, wherein at least a portion of the moisture in the moisture-reduced slurry layer is removed to form a protective stratum on the produce, wherein the second drying procedure includes applying energy from at least one energy source to the produce; and
(3) subjecting the produce to a third drying procedure, wherein at least a portion of the moisture in the protective stratum is removed to form a protective film or layer on the produce, which layer of film includes crystalline structures, wherein the third drying procedure includes applying energy from at least one energy source to the produce.
The present invention, in accordance with a first embodiment of the present invention, there is provided a first apparatus or system for extending the shelf life of harvested produce by removing pathogens from the outermost layer of the produce. The apparatus or system minimally comprises:
(1) a selectively operable first mechanical force assembly for directing a mechanical force to impinge upon the produce;
(2) a selectively operable first energy source assembly for directing a first form of non-mechanical energy at the outermost layer of the produce; and
(3) a selectively operable second energy source assembly for directing a second form of non-mechanical energy at the outermost layer of the produce.
In accordance with a second embodiment of the present invention, a second apparatus is provided for extending the shelf life of produce. The apparatus is preferably used with the produce that has a solute-laden slurry layer applied to at least a portion of the external surface thereof. The apparatus is comprised of at least the following assemblies: (1) a selectively operable air stream assembly for directing an air stream to the produce; (2) a selectively operable first energy source assembly for directing energy to the produce; and (3) a selectively operable second energy source assembly for directing energy to the produce.
In accordance with third embodiment of the present invention, a third apparatus for extending the shelf life of produce is provided. This apparatus is preferably used with produce which has a solute-laden slurry layer applied to at least a portion of the external surface thereof. This apparatus comprises:
(1) a selectively operable air stream assembly for directing an air stream to the produce in order to remove at least a portion of the moisture in the solute-laden slurry layer to form a moisture-reduced slurry layer on the produce;
(2) a selectively operable first energy source assembly for directing energy to the produce in order to remove at least a portion of the moisture in the moisture-reduced slurry layer to form a protective stratum on the produce; and
(3) a selectively operable second energy source assembly for directing energy to the produce in order to remove at least a portion of the moisture in the protective stratum to form a protective crystalline structure on the produce.
In accordance with a fourth embodiment of the present invention, a fourth apparatus for extending the shelf life of produce is provided, which is also preferably used with produce that has a solute-laden slurry layer applied to at least a portion of the external surface thereof. This fourth apparatus includes:
(1) a selectively operable air stream assembly for directing an air stream to the produce in order to remove at least a portion of the moisture in the solute-laden slurry layer to form a moisture-reduced slurry layer on the produce;
(2) a selectively operable first energy source assembly for directing energy to the produce in order to remove at least a portion of the moisture in the moisture-reduce slurry layer to form a protective stratum on the produce;
(3) a selectively operable second energy source assembly for directing energy to the produce in order to remove at least a portion of the moisture in the protective stratum to form a protective crystalline structure on the produce; and
(4) a selectively operable transportation assembly for transporting the produce from the air stream assembly, first energy source assembly, and second energy source assembly.
In accordance with a fifth embodiment of the present invention, there is provided a fifth apparatus for extending the shelf life of produce. Again, the produce preferably has a solute-laden slurry layer applied to at least a portion of the external surface thereof. The fifth apparatus comprises:
(1) a selectively operable vibration assembly for vibrating the produce;
(2) a selectively operable first energy source assembly for directing energy to the produce; and
(3) a selectively operable second energy source assembly for directing energy to the produce.
Other features and advantages of the present invention will be become apparent from the following description and appended claims, taken in conjunction with the accompanying Figures.